PROF EIVIND GRØV | INTERVIEW
have taken place in unlined pressurised tunnels from a couple of hundred metres to a thousand metres. “Air cushion chambers have been built
unlined to pressures of up to 7.5 MPa. So Compressed Air Energy Storage (CAES) – in dedicated rock caverns, unlined and pressurised or chilled – would be easy to build. LPG storage in various combinations of pressure and temperature is similarly practicable. Storing ammonia in unlined caverns is partly within existing capabilities, though you would need to control temperature and pressure to obtain a maximum reduction in its volume. But it has been stored with success in hard rock caverns, and doing so is much less complicated than storing hydrogen. “Hydrogen is widely promoted as a
source of clean energy but storing it underground on the large scale requires very cold temperatures and is fully outside current technology. But it is an active field of research, and I would guess that within ten years we should be able to do that. LNG can be dealt with in steel-lined solutions, but to the extent that is possible unlined, or sprayed concrete-lined solutions are to be preferred. “Pumped storage hydro is another
solution that involves tunnelling, and one that is fully operational in some places.” Can we store CO2
in dedicated man-
made caverns? “That is partly within existing capabilities; we have been looking at it and it is
absolutely feasible. Temperatures in the range minus 55°C to minus 22°C and pressures between 7 bar and 18 bar are the requirements, and it would have to be cost-competitive. There are some challenges to overcome there – for example, how does CO2
interact with water, and with
concrete? “And underground solutions have a great
potential to house the next generations of nuclear power production, though cost and public consensus would be issues here. “We may have to build new caverns
for such things, which takes energy of course, but even so the balance would still be advantageous. And there is the real possibility of re-purposing existing caverns. If we look at the big perspective you can perhaps reuse and convert an existing cavern to a new purpose. There is, in Norway, a research programme that we are trying to put together right now to look at future reuse and multiple-purpose use of rock caverns and tunnels and underground facilities to a much larger extent that we have had before. “We prepared an application to the
Norwegian Research Council on this future use of the underground as a research topic, and we are also looking at it from the perspective of planned development of the main cities in Norway – a master plan for using below-ground space, if you like.” The proposed plan was recently put to
the government to consider for funding. About 20 companies and institutes are in the
consortium proposing the research project which, if it is granted, would last eight years and have a budget of around NKr170 million (£12.5 million) per year. As noted, he loves to see bare rock in
tunnels. “But I do realise that not everyone feels that way. In this project application we have included people with architectural backgrounds, people with psychological backgrounds, people who understand the things that make people actually feel comfortable about being underground. “Size is important. Your new Elizabeth
Line in London has walkways and caverns three times the diameter of the older lines; they are more like cathedrals, much less oppressive, not claustrophobic at all. “And lighting and surface textures matter
also. We can do wonderful lighting effects on, say underground road intersections and roundabouts. “So, when we are using these
professionals who look at things from a different perspective to tunnellers, we can build-in these elements that can make you feel comfortable, and safe, and at ease when underground. Tunnellers should work with architects, with psychologists, with all the other disciplines. It should be one big, unified project.” Grøv is also a visionary for long-distance
tunnels – super-long ones, and super deep. “Long-distance corridors undersea from
Korea to China, across the Bering Strait, joining Japan to Korea… such tunnels could compete with flight routes.
Above: Speaking at China Rock 2024 on experiences from pressurised storages in unlined underground rock caverns PHOTO COURTESY OF CHINA ROCK 2024 August 2025 | 37
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